The present invention relates to an iron-containing protein composition solution which is superior in freezing-thawing stability and low in precipitating tendency when frozen and thawed; a frozen product of the solution; a liquid composition obtained by thawing the frozen product; and a powder obtained by drying the solution or the liquid composition. The iron-containing protein composition solution of the present invention has an excellent adaptability for freezing to storage or transfer it in the frozen state. This composition solution has restrained precipitate productivity in the solution obtained by thawing a frozen product of the composition solution. The composition solution has no astringent taste uniquely possessed by iron. Therefore, the composition solution can be suitably used in production of an iron-enriched food or drink or an iron preparation. This composition solution is also useful for prevention or treatment of anemia.
Since 1975, the iron intake by Japanese has been flat at a sufficiency ratio of about 100% relative to the iron requirement. Iron is important -for maintenance of the homeostasis of human body and is one of the nutrients to be taken with care in meals. The iron sufficiency ratio particularly in young to middle aged women is between 80 to 90%, and the iron shortage in these women is pointed out in xe2x80x9cStatus of National Nutrition, 1998 Editionxe2x80x9d, published by Daiichi Shuppan K. K. Thus, many of the young to middle aged women suffering from iron shortage or anemia are supplementing iron in the form of iron-enriched food or drink or of medicine such as iron preparation or the like.
However, inorganic irons used in iron preparations, such as iron citrate, iron pyrophosphate, iron sulfate and the like generally have an astringent taste or a metallic taste, both uniquely possessed by iron, or have harmful side effects such as damages to stomach, intestines and mucosa in some cases. Heme iron, which is an organoiron, has a problem of possessing a metallic taste, a raw fish-like smell, etc. although it is highly absorbable. Therefore, when the above iron preparations are added to a food or a drink or are used as such, there are cases that the addition amount must be restricted in some cases, often making it difficult to intake the required amount.
Meanwhile, as iron-containing proteins, an iron-lactoferrin complex (Japanese Patent Laid-Open (Kokai) No. 304798/""95), an iron-casein complex (Japanese Patent Laid-Open (Kokai) No. 77793/""97), etc. are known in the form of a composition. These iron-containing protein compositions are free from astringent taste or metallic taste uniquely possessed by iron, have no harmful side effects, and moreover are superior in solubility and thermal stability; therefore, they are suited for use in foods, drinks and iron preparations.
Incidentally, one of the present inventors filed as a co-inventor an Japanese Application No. 89741/99 concerning an iron-whey protein complex, which is published as Japanes Patent Laid-Open (Kokai) No. 279143/2000.
As describe above, iron-containing protein compositions are being used in foods, drinks and iron preparations. However, they may have a problem in generating precipitate when a solution of these compositions is frozen for storage, transfer or the like and then thawed.
One of the objects of present invention is to provide a solution containing an iron-containing protein composition useful for iron enrichment in foods and drinks or as an effective ingredient of iron preparation, which solution has restrained precipitate productivity after freezing and thawing. The other object of the present invention is to provide a frozen product of the above solution and a solution obtained by thawing the frozen product, both useful for iron enrichment in foods and drinks as well as for production of iron preparation.
The present inventors proceeded with a study in view of the above objects. As a result, the present inventors found out that precipitation in a resulting solution by thawing a frozen product of the original solution of the iron-containing protein composition, can be suppressed by adding at least one compound selected from monosaccharides, disaccharides, sugaralcohols, non-reducing saccharides and dextrin to the original solution. The present invention has been completed based on this above findings.
In the present invention, xe2x80x9csuperior in freezing-thawing stabilityxe2x80x9d refers to that, when a sample of an iron-containing protein composition solution is placed in an appropriate container and stored in a frozen state at xe2x88x9220xc2x0 C. for 2 weeks, then the frozen sample is thawed, for example, by contacting the container with a flowing water or by allowing the container to stand at room temperature, and 50 ml of the thawed sample is taken into a 50-ml graduated test tube and subjected to centrifugation at 3,000 rpm for 15 minutes using a centrifuge (Kubota Ks-5000P), the volume of the precipitate generated in the centrifuged sample is 0.5 ml or less. When the volume of the precipitate generated is as small as above, the loss of iron-containing protein by precipitation is suppressed effectively; the thawed solution has a good quality for use in a food, a drink or an iron preparation; and its storability and transferability in a frozen state, etc. can give an improved economic efficiency.
The present invention can provide an iron-containing protein composition solution which has restrained precipitate productivity after freezing and thawing, and superior freezing-thawing stability. The iron-containing protein composition solution according to the present invention has no astringent taste uniquely possessed by iron and, therefore, can be suitably used in production of an iron-enriched food or drink or an iron preparation and is useful for prevention or treatment of anemia.